I care because I don't need to know that it's an Arch derivative. Someone else cares about that bit for me. I press the on button and I get a list of my games to start playing. OS updates are packaged by someone who just wants my list of games to work.
Why do you care about having that particular Arch derivative? Any mainstream distro (except Ubuntu derivatives) are perfectly usable for gaming.
There really is no point in waiting for Valve to drop their own Arch derivative. It won't do anything you can not do right now.